Self-limiting growth of ligand-free ultrasmall bimetallic nanoparticles on carbon through under temperature reduction for highly efficient methanol electrooxidation and selective hydrogenation

We report a self-limiting growth method of ultrasmall Pd-containing bimetallic nanocatalysts supported on carbon through under temperature reduction (UTR). The UTR phenomenon is observed for the (co)reduction of a second base metal precursor (M = Co, Ni, and Zn) below its thermodynamic reduction temperature in the presence of Pd. The origin of the UTR phenomenon lies in the hydrogen spillover of Pd to drive the (co)reduction of the base metal at the temperature below its thermodynamic reduction temperature; while, the further reduction is shut down simultaneously to limit the overgrowth of nanoparticles when forming nanoalloys. Using nitrided carbon as a support, we demonstrate the self-limiting growth of three Pd-containing nanoalloys, including Pd1.7Co, Pd1.6Ni and Pd2Zn, with average sizes around 1.5 nm using UTR. Sub-2 nm Pd-containing bimetallic nanoalloys exhibited excellent catalytic properties in both methanol electrooxidation and selective hydrogenation of cinnamaldehyde.